NAGOYA, Japan—Toyota Motor Corp. and BMW AG said they will expand a technology-sharing pact, the latest sign of a deepening partnership between the two companies.

“By working with BMW we hope to speed up the development and diffusion of fuel cell vehicles, which has required significant investments in cost and time,” said Takeshi Uchiyamada, Toyota’s vice chairman and former head of research and development, said at a press conference in Nagoya Thursday. “This will work to strengthen both companies.”

Japan’s Toyota will provide Germany’s BMW with technical know-how for fuel-cell vehicles that Toyota expects to debut in 2015. They will also work together on a next-generation fuel-cell system expected to be completed by 2020.

Hydrogen-powered fuel cells are a key technology for low-emission vehicles both companies plan to launch.

Mr. Uchiyamada and Herbert Diess, BMW’s top executive in charge of R&D, said the two companies had no plans for a capital tie-up to cement their technical partnership.